1. Field of the Invention
The present invention relates to an image-shake correction apparatus, and particularly to an image-shake correction apparatus that implements image-shake correction in a lens unit used for a virtual system or the like.
2. Description of the Related Art
In recent television broadcasting, a technique has frequently been used in which an actually captured video image captured by a television camera and an electronic video image (CG video image) created by a computer, or the like, are synthesized. As a technique for synthesizing video images, the chroma-key synthesis method is generally known. In the chroma-key synthesis method, a photographic subject that is to be a foreground image of a synthesized video image is captured by a television camera or the like, with, for example, a blue cloth (blue background) as a background. From the resultant video signal, a key signal (an outline signal that indicates the outline of the foreground image) for distinguishing a foreground-image area from a blue-background area is created. Meanwhile, a background image that is to be a background of the synthesized video image is created, for example, by a computer or the like. By cutting based on the key signal the foreground-image area out of the background image and replacing the foreground-image area by the foreground image, the synthesized video image in which the foreground image and the background image are synthesized is created (refer to Japanese Patent Application Laid-Open No. 10-42307 and the like).
In addition, a video image synthesis system (a virtual system), referred to as a virtual studio, has been frequently used in which not only video images are simply synthesized through the chroma-key synthesis method, but also a photographic subject captured actually by a television camera is displayed as if the photographic subject were present in a virtual space (virtual studio) created as an electronic video image.
In a virtual system, a desired virtual space is created by a computer or the like and a virtual camera is arranged within the virtual space. Accordingly, image capturing in the virtual space is implemented virtually by the virtual camera, whereby an electronic video image of the virtual space is created. The capturing conditions for the virtual camera is changed in accordance with the change in the capturing conditions, such as focusing operation, zooming operation, and pan/tilt operation, for a television camera (real camera) that actually captures video images; therefore, a synthesized video image is created that is displayed as if a photographic subject for the actually captured video image were present in the virtual space. In addition, in some cases, the synthesis is implemented in such a way that an actually captured video image is used as a background and an electronic video image is used as a foreground image, or actually captured video images are synthesized.
Additionally, in recent years, an image-shake correction apparatus that corrects an image shake has been used in many cases, due to enhancement of the zoom magnification ratio of a lens unit. An image-shake correction apparatus that is integrally incorporated in a lens unit and an image-shake correction apparatus that is an adapter used, as an auxiliary device, attached to a lens unit are known. For example, an image-shake correction apparatus is known in which, in an image-capturing optical system, a correction lens for correcting an image shake is movably arranged in a direction perpendicular to the optical axis, and when a camera (image-capturing optical system of the camera) is vibrated, the correction lens is driven by a motor in such a way as to cancel the image shake caused by the vibration, thereby correcting the image shake (e.g., refer to Japanese Patent Application Laid-Open Nos. 2001-142103 and 2003-107554 and the like). In addition, image-shake correction methods other than the method in which a correction lens is used that moves in a direction perpendicular to the optical axis. In each image-shake correction method, an image displacement device is provided that displaces optically or electronically the formation position of an image formed by an optical system, in the horizontal or vertical direction within the image formation plane; and image-shake correction is implemented by controlling the amount of image displacement through the image displacement device so as to cancel an image shake.